1. Field of the Invention
The invention relates to an electrophotographic image forming apparatus, and a developing device and a process cartridge for use therein.
The electrophotographic image forming apparatus forms an image on a recording medium by the use of the electrophotographic image forming process. Examples of the electrophotographic image forming apparatus include an electrophotographic copier, an electrophotographic printer (such as a laser beam printer or an LED printer), a facsimile apparatus and a word processor.
Also, the process cartridge may be a cartridge into which charging means, developing means or cleaning means and an electrophotographic photosensitive drum are integrally incorporated, and which is made detachably mountable to the main body of the electrophotographic image forming apparatus. Alternatively, the process cartridge may be a cartridge into which at least one of charging means, developing means and cleaning means and an electrophotographic photosensitive drum are integrally incorporated, and which is made detachably mountable to the main body of the electrophotographic image forming apparatus. Further alternatively, the process cartridge may be a cartridge into which at least developing means and an electrophotographic photosensitive drum are integrally incorporated, and which is made detachably mountable to the main body of the electrophotographic image forming apparatus.
2. Description of the Related Art
In an electrophotographic image forming apparatus using the electrophotographic image forming process, there is adopted a process cartridge system in which an electrophotographic photosensitive member and process means for acting on the electrophotographic photosensitive member are integrally made into a cartridge which is made detachably mountable to the main body of the electrophotographic image forming apparatus. According to the process cartridge system, the maintenance of the apparatus can be done by a user himself without resorting a serviceman and therefore, the operability of the apparatus can be markedly improved. Therefore, the process cartridge system is widely used in electrophotographic image forming apparatuses.
As an example of such a process cartridge, there is known a developing device in which developing means which is one of the aforementioned process means is integrally made into a cartridge. The developing device sometimes adopts a construction in which a developing frame for supporting a developing sleeve or the like and a developer container for containing therein a toner which is a developer have their respective joint portions abutting against each other and ultrasonically welded together.
FIGS. 2, 3 and 4 of the accompanying drawings show an example of a conventional developing device. FIG. 2 is a longitudinal cross-sectional view showing the developing device as it is divided into a developing frame 52 and a developer container 51. FIG. 3 is a view of the developing frame 52 as it is seen from the developer container 51 side (from the direction of arrow III in FIG. 2), and FIG. 4 is a view of the developer container 51 as it is seen from the developing frame 52 side (from the direction of arrow IV in FIG. 2).
As shown in FIG. 4, the joint portion of the developer container 51 to the developing frame 52 is provided with an opening portion 51a for feeding the toner from the developer container 51 to the developing frame 52 therethrough. The opening portion 51a, as shown in FIG. 4, is of a rectangular shape long in the left to right direction when the developer container 51 is seen from the developing frame 52 side. The opening portion 51a is provided with a toner seal member 53 having the surroundings of the opening portion 51a welded thereto so as to cover the opening portion 51a. The toner seal member 53 is torn before the use of the developing device and becomes capable of feeding the toner from the developer container 51 into the developing frame 52.
On the other hand, as shown in FIG. 3, the developing frame 52 is provided with an opening portion 52a for supplying the toner fed out from the developer container 51 to a developing sleeve therethrough. The opening portion 52a is provided in opposed relationship with the opening portion 51a of the developer container 51, and is substantially equal in size to the opening portion 51a of the developer container 51.
As shown in FIG. 3, welding ribs 52b and 52c ultrasonically welded to the developer container 51 are provided in the respective vicinities of the upper and lower end portions of the developing frame 52. The two welding ribs 52b and 52c are straight and are disposed substantially parallel to each other along the lengthwise direction of the opening portion 52a. Convex bosses 52d and 52e for positioning the developing frame 52 relative to the developer container 51 are provided on the lengthwisely opposite end portions of the upper welded rib 52b. Also, in order to prevent the leakage of the toner from between the developing frame 52 and the developer container 51, seal members 55 and 56 formed of elastomeric foam are attached to the lengthwisely opposite end portions of the developing frame 52.
On the other hand, as shown in FIG. 4, the developer container 51 is formed with welding grooves 51b and 51c at locations opposed to the welded ribs 52b and 52c of the developing frame 52. The two welding grooves 51b and 51c are straight, and are disposed substantially parallel to each other along the lengthwise direction of the opening portion 51a. Positioning holes 51d and 51e fitted onto the bosses 52d and 52e, respectively, provided on the developing frame 52 are formed in the lengthwisely opposite end portions of the upper welding groove 51b. 
The developing frame 52 and the developer container 51 are positioned relative to each other by the bosses 52d, 52e and the positioning holes 51d, 51e being fitted together, and thereafter as shown in FIG. 2, ultrasonic vibration is applied thereto while the backs 52f and 52g of the surfaces on which the welding ribs 52b and 52c of the developing frame 52 are provided and the backs of the surfaces in which the welding grooves 51b and 51c of the developer container 51 are provided are pressed, whereby the welding ribs 52b and 52c are melted and welded to the welding grooves 51b and 51c, respectively, of the developer container 51.
In the above-described conventional construction, however, if the welding condition is too strong during ultrasonic welding, the unevenness of the melting of the welding ribs increases and therefore, the developing frame becomes liable to be deformed. This has led to the possibility that the positional accuracy of parts attached to the developing frame may be reduced or the positional accuracy of the developing device and the image forming apparatus may be reduced, whereby the quality of printing may be reduced. Also, by making the energy applied during ultrasonic welding small in order to avoid such possibility, there have been posed the problem that the strength of welding is reduced or the setting of the welding condition becomes difficult, and the problem that the cost for raising the accuracy of parts is increased.
It is an object of the present invention to provide a developing device, a process cartridge and an electrophotographic image forming apparatus provided with a frame structure having sufficient welding strength.
It is another object of the present invention to provide a developing device, a process cartridge and an electrophotographic image forming apparatus provided with a construction suffering little from frame deformation during ultrasonic welding.
It is another object of the present invention to provide a developing device, a process cartridge and an electrophotographic image forming apparatus provided with a construction which is high in the positional accuracy of developing means supported by a developing frame.
It is another object of the present invention to provide a developing device, a process cartridge and an electrophotographic image forming apparatus provided with a construction having a welding rib with which a developing container and developing frame are connected together by ultrasonic welding, the welding rib being provided on a joined surface opposite from a surface on which a plurality of reinforcing members are provided, and the plurality of reinforcing members provided along a lengthwise direction of the developing frame with spacing between them in a direction intersecting the lengthwise direction to increase the strength of the developing frame, the welding rib being provided between the plurality of reinforcing members.
These and other objects, features and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.